1,1-Dichloro-2,3,3,3-tetrafluoropropene (CFO-1214ya) is a compound useful as a synthetic raw material for 2,3,3,3-tetrafluoropropene (HFO-1234yf) which is expected in recent years as a new refrigerant to be substituted for 1,1,1,2-tetrafluoroethane (HFC-134a) being a greenhouse gas. In this specification, with respect to a halogenated hydrocarbon, the compound name may be followed by an abbreviated name of the compound in parenthesis, but in this specification the abbreviated name may be employed instead of the compound name, as the case requires.
As a method for producing such 1,1-dichloro-2,3,3,3-tetrafluoropropene (CFO-1214ya), a method has been known wherein, as a raw material, 1,1-dichloro-2,2,3,3,3-pentafluoropropane (HCFC-225ca) is dehydrofluorinated by an aqueous alkali solution in the presence of a phase transfer catalyst or by a gas phase reaction in the presence of a catalyst such as chromium, iron, copper or activated carbon (Patent Document 1).
Here, 1,1-dichloro-2,2,3,3,3-pentafluoropropane (HCFC-225ca) to be used as a raw material in the above method is usually produced in the form of a mixture with 1,3-dichloro-1,2,2,3,3-pentafluoropropane (HCFC-225cb), 2,2-dichloro-1,1,3,3,3-pentafluoropropane (HCFC-225aa) and/or other dichloropentafluoropropane isomers (Patent Document 2, Non-Patent Document 1), and therefore, one separated and purified from such a mixture of isomers has been employed as a raw material in the above production method.
However, with respect to the above dichloropentafluoropropane isomers, their boiling points are rather close to one another, whereby their separation and purification are difficult by a usual separation/purification technique (such as distillation), and in order to produce highly pure 1,1-dichloro-2,2,3,3,3-pentafluoropropane (HCFC-225ca) on an industrial scale, a multi-stage distillation, etc. are required.
When the production is comprehensively considered including the preparation of the raw material, etc., the above-mentioned conventional method for producing 1,1-dichloro-2,3,3,3-tetrafluoropropene (CFO-1214ya) can hardly be regarded as a simple and economical production method.